Why does the retaining ring fix the shaft?

A retaining ring, also known as a snap ring or circlip, is used to fix a shaft in place within a mechanical assembly by providing a secure and reliable method of axial retention. Here's how a retaining ring accomplishes this:

Groove Placement: To use a retaining ring effectively, a groove is typically machined or formed into the shaft. This groove is designed to accommodate the retaining ring.

Radial Expansion: Retaining rings are circular and have a slightly smaller diameter than the shaft they are meant to retain. They are manufactured with a small gap (known as the ring's "free diameter") between the two ends of the ring.

Installation: When installing an external retaining ring, for example, it is placed over the end of the shaft and pushed down into the groove. As it enters the groove, the retaining ring is compressed slightly, which causes it to exert an outward radial force against the walls of the groove.

Retention: The outward radial force exerted by the retaining ring ensures that it remains seated securely within the groove. This force prevents the shaft from moving axially, or in other words, it prevents the shaft from sliding in or out of the assembly.

Security: Because the retaining ring is held firmly in place within the groove, it effectively locks the shaft in its axial position. It acts as a barrier, preventing the shaft from unintentional movement due to vibrations, axial loads, or other external forces.

In summary, the retaining ring fixes the shaft by utilizing its radial expansion properties and the groove in the shaft. The ring's outward radial force keeps it engaged within the groove, ensuring that the shaft remains securely in place and cannot move axially. This is a simple yet effective method for retaining and securing shafts within mechanical assemblies.